添加外键（MySQL）时出错（错误代码1215）

我试图在两组不同的表之间添加一个外键，第一组是customer和shopping_cart。我试着看了其他关于这个错误的帖子，但是看了之后我没能让它起作用

CREATE TABLE `usale`.`customer` (
CREATE TABLE `usale`.`customer` (
`customer_id` SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
`first_name` VARCHAR(45) NOT NULL,
`last_name` VARCHAR(45) NOT NULL,
`email` VARCHAR(50) NULL DEFAULT NULL,
`active` TINYINT(1) NOT NULL DEFAULT TRUE,
`create_date` DATETIME NOT NULL,
`last_update` TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP,
`student_student_id` BIGINT NOT NULL,
`student_school_id` BIGINT NOT NULL,
`shopping_cart_cart_id` TINYINT UNSIGNED NOT NULL,
PRIMARY KEY (`customer_id`, `student_student_id`, `student_school_id`)),
INDEX `fk_customer_student1_idx` (`student_student_id` ASC,`student_school_id` ASC),
INDEX `fk_customer_shopping_cart1_idx` (`shopping_cart_cart_id` ASC),
CONSTRAINT `fk_customer_student1`
FOREIGN KEY (`student_student_id`)
REFERENCES `usale`.`student` (`student_id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION,
CONSTRAINT `fk_customer_shopping_cart1`
FOREIGN KEY (`shopping_cart_cart_id`)
REFERENCES `usale`.`shopping_cart` (`cart_id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION)
ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;`customer_id` SMALLINT UNSIGNED NOT NULL AUTO_INCREMENT,
`first_name` VARCHAR(45) NOT NULL,
`last_name` VARCHAR(45) NOT NULL,
`email` VARCHAR(50) NULL DEFAULT NULL,
`active` TINYINT(1) NOT NULL DEFAULT TRUE,
`create_date` DATETIME NOT NULL,
`last_update` TIMESTAMP NULL DEFAULT CURRENT_TIMESTAMP,
`student_student_id` BIGINT NOT NULL,
`student_school_id` BIGINT NOT NULL,
`shopping_cart_cart_id` TINYINT UNSIGNED NOT NULL,
PRIMARY KEY (`customer_id`, `student_student_id`, `student_school_id`))


CREATE TABLE IF NOT EXISTS `frankapp`.`shopping_cart` (
`cart_id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
`last_update` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
`cart_total` DECIMAL(12,2) NULL,
PRIMARY KEY (`cart_id`))
ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;

ALTER TABLE customer ADD CONSTRAINT `fk_customer_shopping_cart1`
FOREIGN KEY (`shopping_cart_cart_id`)
REFERENCES `usale`.`shopping_cart`(`cart_id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION

我得到一个错误：“错误：无法添加外键约束 错误代码：1215“

对于第二组表，它们被命名为shopping\u cart和shopping\u cart\u item

CREATE TABLE IF NOT EXISTS `usale`.`shopping_cart_item` (
`shopping_cart_item_id` BIGINT NOT NULL,
`shopping_cart_cart_id` TINYINT UNSIGNED NOT NULL,
`inventory_item_inventory_item_id` BIGINT UNSIGNED NOT NULL,
`inventory_item_student_id` BIGINT NOT NULL,
`inventory_item_inventory_type` VARCHAR(45) NOT NULL,
`inventory_item_student_student_id` BIGINT NOT NULL,
`inventory_item_student_customer_id` BIGINT NOT NULL,
`inventory_item_student_school_id` BIGINT NOT NULL,
`inventory_item_edition_edition_id` BIGINT UNSIGNED NOT NULL,
`inventory_item_edition_author_id` BIGINT NOT NULL,
PRIMARY KEY (`shopping_cart_item_id`, `shopping_cart_cart_id`, `inventory_item_inventory_item_id`, `inventory_item_student_id`, `inventory_item_inventory_type`, `inventory_item_student_student_id`, `inventory_item_student_customer_id`, `inventory_item_student_school_id`, `inventory_item_edition_edition_id`, `inventory_item_edition_author_id`),
INDEX `fk_shopping_cart_items_shopping_cart1_idx` (`shopping_cart_cart_id` ASC),
INDEX `fk_shopping_cart_item_inventory_item1_idx` (`inventory_item_inventory_item_id` ASC, `inventory_item_student_id` ASC, `inventory_item_inventory_type` ASC, `inventory_item_student_student_id` ASC, `inventory_item_student_customer_id` ASC, `inventory_item_student_school_id` ASC, `inventory_item_edition_edition_id` ASC, `inventory_item_edition_author_id` ASC))

CREATE TABLE IF NOT EXISTS `frankapp`.`shopping_cart` (
`cart_id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
`last_update` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
`cart_total` DECIMAL(12,2) NULL,
PRIMARY KEY (`cart_id`))
ENGINE = InnoDB
DEFAULT CHARACTER SET = utf8;


ALTER TABLE shopping_cart_item ADD CONSTRAINT `fk_shopping_cart_items_shopping_cart1`
FOREIGN KEY (`shopping_cart_cart_id`)
REFERENCES `usale`.`shopping_cart`(`cart_id`)
ON DELETE NO ACTION
ON UPDATE NO ACTION

我再次遇到错误1215：“错误：无法添加外键约束

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错误代码：1215“

若您引用外键约束中的任何表，则表创建顺序在此处起作用，这意味着该表必须已创建。因此，请对create语句重新排序。我已经创建了没有外键约束的表。我试图在事后添加它们，所以所有的表都被创建了。或者我应该删除这些表并以不同的顺序创建它们？